A tube-shaped lamp, normally fluorescent, is known having at each end a pair of connector pins that extend axially at a standardized spacing. These pins allow the lamp to be powered when it is on and allow it to be ignited at the start of use, typically by applying a short-duration high-voltage burst between two of the pins.
The standard medium bipin base has been replaced with several other formats that correspond to lamps operating at different starting and operating voltages. Thus, although the pin spacing and length is normally the same, the pins are differently shaped so that, in theory, a lamp cannot be fitted to a fixture that is not adapted to run it. Thus while a medium bipin base has two cylindrical pins of uniform cross-sectional size, a G5 base has two pins of flattened or oval section that may be formed with grooves. Fitting a fixture with a lamp that is supposed to be started with or operate at a different voltage can lead to damage not only to the lamp, but to the fixture.
Thus it is the responsibility of the manufacturer of the lampholders to produce them in the different sizes required by the different lamps. This poses a manufacturing and inventory problem as, not only must the different holders be produced according to different specifications, but they must stocked, marketed, and cataloged individually. The obvious result is to increase the cost of the lampholders, produced in huge quantities by mass production, thereby raising the costs of the fixtures they are incorporated into.